So security wise in POW, computational power is used to solve the algorithms then the transaction is added to the block making the chain of blocks more secure and the transactions data cannot be changed same in POS but in POS the rich party will have the more influence as they lock their funds as safety. Means POW provides more security and by environmental aspect wise, POW is criticized more because for POW we need high computational power and for that we need specific builds and GPUs which eats away a lot of electricity and consume high energy cause environmental pollution and misuse this also lead the POW mining to many scrunties.

But POS is environmental friendly and that's why it never got scrunted over the green ecosystem excuse. And POS are usualy faster but POW has its own level in the market and POW of BTC is slow then POS of ETH but POW still a king.

I can't say you missed it up but
Let's see
Bitcoin is decentralized because it uses POW rather than proof of stake.
The computation makes it that a person can't centralized the system and the only centralization that could come up is Mining pool centralization.
While POS, that's purely centralized
The richer you are, the richer you get
And it continues.
POW is more secured but sacrificed energy and scalabilty for security and decentralization
But the opportunity cost are been mitigated by Layer 2 network like Lightning.